Fireplace inserts that can be fitted into a pre-formed cavity built into the wall of a dwelling are well known. Examples of various inserts can be found in the following patents:
U.S. Pat. No. 4,519,376 to Schoeff et al PA1 U.S. Pat. No. 5,009,219 to Liet PA1 U.S. Pat. No. 3,842,821 to Juris PA1 U.S. Pat. No. 4,683,623 to Cannata PA1 U.S. Pat. No. 4,793,322 to Shimek et al PA1 an enclosure dimensioned to be insertable within the fireplace cavity to define a combustion chamber for generating heat; PA1 manifold means for distributing fresh air from the fresh air inlet to the combustion chamber, the manifold means being positionable at a predetermined location within the fireplace cavity according to the position of the fresh air inlet; and PA1 connection means for communicating the combustion chamber with the combustion gas outlet.
In many cases, the fireplace inserts are direct vent inserts that receive outside air for combustion through a fresh air inlet and vent combustion gases through a venting passage or outlet. Generally, the inlet and outlet comprise tubular ducts that are arranged co-axially such that the heated combustion gases pre-heat the outside fresh air. Often the inlet and outlet ducts extend upwardly from the fireplace cavity. This top vent configuration is common when the insert is used within an old fireplace cavity that vents through the existing chimney structure. Alternatively, the fireplace insert can be vented by an inlet and outlet extending rearwardly from the insert through the building wall to the outside in a rear vent configuration.
Fireplace inserts are generally of modular construction to allow for quick adaptation or modification of the basic insert unit to fit into the large number of the fireplace cavities that would normally be encountered. However, there is still the need to have on hand at least two outer fireplace shells to accommodate the top vent and rear vent configurations leading to additional inventory and storage costs.
A previous solution to this problem involved a hybrid outer shell design having an upper and lower connection extending from a rear surface of the fireplace insert angled at 45 degrees. The upper connection is used when the unit is installed in a cavity having top venting and the lower connection is used when the unit is installed in a rear vent cavity. In either case, the unused connection would be blocked off. This solution is wasteful of materials since each fireplace insert includes a connection that will not be used.